Profiles for windows and doors need to meet high mechanical requirements to withstand side forces applied on the door or window by for example wind and have high thermal insulation requirements in for preventing energy losses through a window or door frame made of these profiles.
For large glass areas or for applications exposed to wind or windows being mounted non-vertically, the mechanical properties of frames made of thermoplastic profiles can be insufficient. For this reason, polymeric profiles often comprise a stiffening chamber for accommodating a stiffening member, such as a ceramic or metal profile as disclosed e.g., in DE102008015102, DE19925495, DE202005004616, or a foam such as in DE102005021934. Such solutions have a number of drawbacks. First, a metal stiffening profile inserted into a stiffening chamber of the polymeric frame forms a thermal bridge which is detrimental to the thermal insulation properties of the frame. Second, inserting such stiffening profiles is extremely labour intensive which weighs heavily on the production cost of the frame. Third, the shape of the stiffening chamber may differ from one model of polymeric profile to another, requiring complex storage management of stiffening profiles of different geometries.
In order to solve some of the above problems, it has been proposed to reinforce window frames with an external reinforcement add-on coupled to an external, visually apparent surface of the window frame. This solution has an obvious aesthetic drawback that few consumers are ready to accept. An example is disclosed in DE102005021934 wherein an external metal profile is clipped to a polymeric frame.
Polymeric window and door frame profiles typically have one or more finished outer side surface portions and one or more technical outer side surface portions, whereby the finished side surface portions are those that are exposed, i.e. visible, when the window or door is installed, while the technical side surface portions are facing a wall, other profile or pane of the door or window and hence are not exposed, not visible, when the window or door is installed. These technical side surface portions usually comprise a more complex structure of brackets and guides for accommodating window or door hardware.
The technical side surface portion of a window sash profile facing a glass pane usually comprises two opposite brackets extending in a longitudinal direction of the profile. A multitude of designs is available on the market, but usually one bracket is an integral part of the sash profile, forming a ledge on which to lay a window pane before clamping it by clipping in place the second bracket. A drainage zone in the form of a channel extending along said longitudinal direction is created between, on the one hand, said pair of clamping brackets and, on the other hand, the edge of the pane and the adjacent external surface of the frame comprised between said pair of brackets. Said channel is often used to accommodate an insert. For example in EP1288426 an insert is used to support and hold a security glass pane in a window or door frame. Similarly, DE102005021934, DE19956441, EP1164248, FR2725753 and EP2052125 disclose a support insert positioned in such channel to hold the glass pane in place. EP1911923 discloses an insert improving (decreasing) the thermal conductivity of a window frame.
The present invention provides a solution for stiffening a polymeric frame profile for a window or door obviating the above mentioned problems. In particular, a stiffing profile is presented which has no detrimental effect on the thermal insulate properties of the profile and which is aesthetically acceptable for the consumer in that it is not or hardly visible from the exterior of a closed and installed door or window. The stiffening profile can be applied in plant or in situ, even after the various profiles are cut and welded to form a frame for a given application, and it can be applied where reinforcement is needed only. Furthermore it is very cost effective. This and other advantages of the present invention are presented in continuation.